In many industries various processes, equipment and loads have a need for a constant force to provide the necessary support as the equipment or loads undergo weight, spatial and/or thermally-induced changes or displacement. A constant force acts to counterbalance the changes or displacements and enables the supported item to move, for example, vertically or horizontally, without a change to the supporting force.
For example, one such constant force requirement is the field support for thermally changing equipment, such as support for piping associated with a tall cracker unit (i.e., high temperature vessel). During periods of shutdown, the unit cools, and the piping attached to the top of the unit may not be at the same or similar temperature as the associated unit. As the unit cools and contracts, a movement is imparted to the associated piping. In some cases, this movement can be quite large (in some cases up to ten (10) inches). Since the piping is connected to the unit, the piping must follow the motion occurring at its point of connection, or face tear or rupture at or near the connection point. Because of the possibility of movement, the entire piping system requires an independent and known force to support its weight. The weight of the piping is fixed, so the force needed to support the piping is also fixed. If the unit thermally expands and imparts motion to the associated piping system and the constant force generator may be fouled or corroded, preventing its proper operation and the piping may be subjected to adverse and damaging stresses that could lead to premature and catastrophic piping failure.
Existing constant force technologies used to load balance include conventional large coiled type spring system and components which are machined and welded together to form one constant force unit, such as shown in FIG. 1. These technologies require large and heavy geometric configurations to drive the spring system. The machined and welded constant force unit requires extra attention and care of component alignment, machining time and tolerances during production.
Using existing constant force systems, a specific fixed geometric configuration is required for each load rating, such as shown in FIG. 6A. A specific constant force unit is required for a specific load rating, thus each unit has to be precisely fabricated, assembled and inventoried. With well over one hundred published load ratings, current art requires significant warehousing and fabrication demands and associated longer lead times to support a growing demand for the existing technologies.
Additionally, due to the use of large coiled spring systems and the associated support geometry, as well as fabrication procedures, a large number of unit configurations are required to support a wider range of unit loadings. Hence, to change output force values that might be necessary due to external process changes or displacements, a complete unit change-out may be required. The use of different units to support differing loadings may require a large stock of unit configurations to be held in inventory, thereby imposing costly warehousing requirements.
Existing constant force spring generating systems expose critical internal components, such as the spring coils, to adverse environmental conditions, as shown in FIG. 2. Often, the result of an exposed force spring generating system is a degradation of system performance due to component corrosion and fouling of the force generating system (i.e., spring coils) caused by corrosion, air-borne foreign particulates, and rain, snow, ice, or wind over time. The exposure of these internal systems may serve to reduce their useful life expectancy, degrade system performance over time, as well as negatively impact system safety. These systems may require significant ongoing maintenance, cleaning and/or replacement due to the corrosive damage, fouling and other environmental factors. Also, an exposed force spring generating system may limit the usefulness of such a system for use in undersea or under water applications where significant water corrosion damage may occur.
A need exists for a constant force generator with a single geometric configuration and interchangeable component design that can service a wide range of loads undergoing weight, spatial and/or thermally-induced changes or displacement. A need also exists for a constant force generator whose critical components are sealed, thereby minimizing its exposure to unfavorable environmental conditions. A need also exits for a smaller, less bulky, more compact constant force generator than current technologies.